The UK show's 50th anniversary special offers a golden opportunity to celebrate a program that spans generations and countries.

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Matt Smith (l.) as the eleventh Doctor and David Tennant as the tenth Doctor in the "Doctor Who" 50th Anniversary Special airing Saturday on BBC America.

Saturday marks the 50th anniversary of "Doctor Who," the British TV gem that chronicles the journeys of a quirky, time-and-space traveling do-gooder. But truth be told, on this side of the Atlantic, major interest in the Time Lord’s trip clocks closer to eight years.

That's how long it’s been since a succession of new doctors and top writers, led by Steven Moffat, revived the program, 16 years after its original 1963-1989 run. The recharge not only boosted “Doctor Who” to new creative heights, but elevated the show from a very modest cult fan base in the US to a devoted following that’s growing far beyond the proud Comic-Con crowd.

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Now Saturday’s 50th anniversary special is slated to air simultaneously in 75 countries, which may prove to be the Doctor’s greatest time bend of them all. The episode marks a golden opportunity to celebrate a program that spans generations and the world.

We got a taste of the global extent of Who-mania earlier this year with the live, international broadcast revealing Peter Capaldi as the 12th Doctor (he’s set to replace Matt Smith with the upcoming “Doctor Who” Christmas special). The announcement, which arrived on a Sunday in the dead of August, sparked online and TV hoopla. “Doctor Who” is a show worth tweeting about, and major developments make big social media news.

The BBC’s decision to broadcast Saturday’s special around the world in one shot – as well as offering theatrical and TV 3D versions – also highlights the silliness of delaying the US broadcast of another UK favorite. Many of us are struggling to avoid an Internet brimming with “Downton Abbey” spoilers as we wait for the Season 4 premiere on PBS in January, four months after its ITV debut.

It’s been a tough enough wait since the most recent installment of “Doctor Who” six months ago. The special tries to make up for the lag by offering a meeting of the two most recent Doctors – played by Smith and David Tennant – along with a mysterious “War Doctor” portrayed by John Hurt. That’s bound to sound confusing to the uninitiated – and perhaps even to some latter-day Whovians. But personnel complications are part of the charm of a show in which the star changes every few seasons, as the Doctor regenerates into a new body.

That gimmick has contributed to the endurance of “Doctor Who,” whose premise has remained largely the same since it premiered on Nov. 23, 1963, a day after the Kennedy Assassination and as Beatlemania roared through the UK before hitting the US 2 ½ months later. The delay for “Doctor Who” in gaining a US foothold proved far longer. Saturday’s special bodes to solidify the “Who” universe’s place in the global popular culture.

At this point, anyone with access to the Internet or cable likely is at least familiar with the word “TARDIS” – the Doctor’s time-and-space traveling machine, housed in an old British police box. Most have probably seen – or, more likely, heard – Daleks, the lumbering, fire-hydrant-shaped villains who spout a distorted, Auto-Tune-like growl of "Exterminate!"

The Doctor’s job is to keep us from being exterminated. He’s not technically human, but looks it, and generally acts it. His rotating band of human companions is the heart of the show and serves as an audience surrogate. The two-hearted Gallifrey native cares about our world – and many others.

There’s been an understandable temptation over the years to call “Doctor Who” a kind of British “Star Trek.” At least on the surface, the description skims the mark: Both shows rose in the 1960s and used science fiction to tell contemporary stories. Both have endured in popularity, via new versions and cast changes that have spurred furious fan debates over who is the best doctor or starship captain. But the franchises ultimately are very different trips.

“Doctor Who” plays largely in the mind, even if the special effects are far better now than a half-century ago. Still, we’ve never seen the show’s most frightening villains – the relatively low-tech, stone Weeping Angels – actually move.

There’s plenty of action in the preview for the special, appropriately titled, “The Day of the Doctor.” Check out the clip below as the world awaits a “Doctor Who” installment for the ages: